Oil coming out of vent hose

6 replies to this topic
  • Ryan426

Posted February 09, 2010 - 01:56 PM


I bought an '01 YZ426 and did an oil and filter change the other day. I put in just over a qt. and a 1/2. Now I have oil coming out of the hose on the bottom left side of the eng. I belive it's the vent hose. Is this normal or did I f something up?? Pleaser help.....:ride:

  • grayracer513

Posted February 09, 2010 - 02:04 PM


I'll bet you only removed one drain plug, am I right? If so, it's overfilled.

Read the following link:

Yours being a 426, the following 3 items will differ:

  • The location of the sump drain plug. It will still be in the same area under the trans, just slightly different
  • The point at which the oil is filled will be at the dip stick on top of the frame, not on the mag cover.
  • The amount of oil will be 1.5 L (1.32 Imp qt, 1.59 US qt) without an oil filter,
  • with oil filter replacement 1.6 L (1.41 Imp qt, 1.69 US qt)

  • Ryan426

Posted February 09, 2010 - 07:26 PM


I removed the one in the frame and under the motor and filter.

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  • grayracer513

Posted February 09, 2010 - 08:42 PM


And what does the oil level look like on the dip stick, then? (Be sure you check AFTER the engine has been run for a minute, then shut down)

  • tp3dxf

Posted February 10, 2010 - 12:37 AM


I removed the one in the frame and under the motor and filter.

You did it Exactly how your supposed to do.

The hose your seeing oil seep out of is a vent hose off the top end. It's normal to get a few drips out of it when you park the bike or let it sit for a while. I've actually pinched the hose and blew out a top end rubber gasket. Not good in the middle of the dez. But with a couple of wrenches I was able to put it back and ride another 2500 miles. Not all on that day of course. What your seeing is totally normal for a early WR.

I think the proper name is Breather they will collect oil and drip. My 01 did it and so did all of my friends it looks worse then it is. Seems like a lot of oil but it isn't much. Never had to add oil between oil changes. Just one of the many quirks of the early WR's. Great bikes then and now.

Edited by tp3dxf, February 10, 2010 - 01:03 AM.

  • myoung

Posted February 10, 2010 - 09:51 AM


Like any open breather system, even on cars, there will be a small amount of oil that migrates it's way into and out the hose. What is a problem is a lot of oil. This can be from it being overfilled, or excessive blow by. You say you pulled both plugs and the filter, so a little over a quart and a half shouldn't be overfilled.

My '00 426 has about 400 hours now on the original top end and oil flow from the tube has increased as the blow by has increased from wear and tear. I also have to check and top off the oil more often because of this. Do you know how much time is on your bike?

  • Ryan426

Posted February 12, 2010 - 04:45 AM


I have no idea how many hours are on this bike. I'm the 3rd owner.

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